APPARATUS AND METHOD FOR REGULATING THE CROSS-LINKING DENSITY OF GLASS COATINGS

Abstract: Apparatus and method for measuring and regulating the cross-linking density in the hot and cold treatments of lightened glass, based on measuring the reflection of polarized radiation emitted by the treatment. The apparatus comprises a base for setting the angles and planes of polarization and incidence, with a head for the emission and reception of the polarized radiation; a central unit for amplification and processing of the received signal, with control of the treatment dosage; and a printer for recording the results obtained.

Description: The present invention relates an apparatus and method for measurement and control of the metering out of compounds to be crosslinked in heat and cold treatments for obtaining lightened glass. DESCRIPTION OF THE PRIOR ART In obtaining lightened glass, a series of treatment materials are used, at various points on the production line, metering out products (which generally deposit tin or titanium dioxides, etc.) which, on being deposited on the surface of the glass, confer on it properties (with respect to impact resistance, resistance to pressure and to wear) which are superior to an untreated glass of the same thickness. These treatment materials make it possible to obtain a glass which is 40% lighter and with up to 50% higher impact resistance, giving rise to the importance of the measurement and control of the metering out of these treatment materials. Techniques are known for detection of defective glass containers by thermal shock (US4733973) or by means of variations in pressure pulses (US4899573), or techniques including those which use complex optical systems for determining shapes, volumes, cracks, presence of adhesives and geometrical defects (ES531750, ES539594, US4778999). None of these systems have anything in common with the one described here, neither as to its purpose, nor due to the means used. The majority of these systems are not adapted to production lines, nor especially designed to detect faults in the treatments for covering crystal containers, nor give rise to the possibility of controlling the manufacturing process automatically, on the basis of the detected values. They behave in that regard as laboratory quality checks. Currently, from the point of view of the manufacture of treated glass, the said treatment is controlled by means of the manual collection of specimens, approximately every 6 hours, determining their concentration in the laboratory and carrying out manual regulation of the speed of the metering pumps so that the metering out is maintained at the desired value. As the conditions of the treatments are not constant, these operations have to be carried out throughout the entire manufacturing process, which is continuous for 24 hours a day and all year long (except for changes in production format). All this means that actually maintaining reliability in the average quality of the manufactured product is impossible, and that faults in the quantity of treatment material deposited, with the consequent loss of properties, have a considerable added cost (remelting energy, costs of manufacture, palletizing and transport etc.). From the point of view of the user (packagers etc.) the defective object is generally discovered because the product gets scratched during handling, breaks due to slight impacts and bursts under pressure when there is a lack of treatment, while, if there is an excess of treatment material deposited, the surface of the glass takes on a metallized appearance which is inappropriate for presentation, especially of food products and drinks. The compounds used in the treatments do not form a continuous sheet on the glass, but a non-uniform cross-linked surface distribution, for which reason it is impossible to talk of measurements of the covering thickness, but rather of average concentration per unit of surface area, on which the properties which the glass acquires with these treatment materials will depend. DESCRIPTION OF THE INVENTION The apparatus and the method, which are the subject of this invention, allow reliable and automatic determination and regulation of the average quantity of treatment material deposited, as well as its manual and point-like, linear or surface utilization, for use in the laboratory or on a production line. The apparatus of the invention is defined in claim 1 and the method of the invention is defined in claim 14. The method proposed is based on the determination of the quantity of treatment material deposited by means of the measurement of the quantity of radiation reflected by the treatement material deposited on the surface of the glass. If radiation is made to fall on treated glass (radiation of any wavelength and type) we will obtain a reflection due to there being a change in propagation medium (air-glass); some of this reflection will be due to the glass itself and some to the treatment material deposited. Since for small values of treatment the quantity reflected by the glass is quantitatively more important, and, moreover, since this is not constant as it depends above all on the surface roughness, in order to be able to obtain a reliable measurement, from the lowest values, it is necessary as far as possible to eliminate or attenuate the reflection due to the glass without affecting that due to the treatment material deposited. This is achieved in the invention described by polarizing the radiation from the emitter in a plane which is polarised in a plane perpendicular to the plane of incidence and choosing the angle of incidence, so that the measurement of the reflection will be due solely to the treatment material crosslinking. In the invention, the head may consist of a colocated emitter and receiver together forming the angle of polarization of the glass with the normal to the surface of the glass, plus a polarizing system located in front of the emitter, or a polarized radiation emitter, which allow polarization of the radiation in a plane perpendicular to the incidence plane. The apparatus can be used in the laboratory for perimetral surface or linear point-like measurements, or on the production line for serial measurements. The rest of the components of the apparatus of this invention consist of: 1) A plinth or frame, for locating and self-centring the object to be measured, which makes it possible to control the angles of incidence and reflection as well as the normal to the measurement surface. This plinth also contains a cover with a pressure shoe. The corresponding head and its suspension system which make it possible to remain in continuous contact with the surface of the glass both when at rest and when moving. Both the head and the centring elements of the plinth are free to move, movement being adjustable in speed and direction in order furthermore to allow point readings, longitudinal readings, perimetral and spiral readings (of variable pitch according to the speed which the head is given) in a manual or automatic process, and motorized in both cases 2) The central unit which drives the emitter of the head intermittently in order to eliminate the effect of ambient radiation, with which the receiver alternately picks up an ambient signal and immediately after an ambient signal plus the measurement signal; both signals are taken to a logarithmic amplifier which amplifies the signal and sends it to a microprocessor which forms the difference between the two values and stores the result. The visual measurement indicator, which may be pointer-type or digital (merely indicative in the case of production lines). The metering control circuit, where the received signal is inverted, given that the correction, in terms of the metering speed of the pumps, is inversely proportional to the quantity of treatment measured. The control circuit has been assigned an (adjustable) signal of the "standard of the treatment material deposited" value which it is desired to obtain. This signal is used so that the apparatus is regulated at the moment of switch-on and as a signal for comparison with the mean received from the microprocessor. Depending on this comparison, another part of the control circuit corrects the treatment material delivery signal which the metering pump receives so that the value of the treatment material delivered is the standard one. This circuit stores the appropriate speed in memory until the next measurement and generates the corresponding signal which determines the metering speed of the pump. Thus by successive approximations, in order to avoid abrupt jumps in the metering speed, deviations in the chosen standard value are corrected, despite the variations in the treatment material and production conditions. At the end of the selected measurement process, the arithmetic mean of all the differences (actual measurements) which are stored is obtained, and the mean obtained is downloaded onto: 3) A printer connected to the central unit, where the program of the microprocessor shows the data on: company (assigned), production line number (assigned), date, time and treatment method; with which it is possible to produce and check graphs of production quality per line, without the necessity for continuous inspections, and to be aware when and which object produced is not within the desired values, if any. For the apparatus intended for use in a laboratory or for determination solely of the average quality with respect to the treatment material deposited on the object which is being purchased, the metering control circuits do not come included in the central unit, and there may or may not be a connection for the printer. The limitation on the number of checks per hour carried out by the apparatus is more dependent on whether the object checked is reincorporated into the production line or discarded, since, on average, the apparatus takes less than 30 seconds to carry out all its functions, for a reading obtained from 300 signals collected in the measurement process. EXPLANATION OF THE FIGURES Figure 1: Elevation view of the plinth Figure 2: Plan view of the plinth Figure 3: Front view of the central unit Figure 4: Printer side view Figure 5: Printer plan view Figure 6: Block diagram EXPLANATORY EXAMPLE 1 The apparatus has all the cables from the central unit interconnected with the plinth and the printer, the central unit and printer are plugged in to a power point, and the switch (1) of the central unit (Figure 3) and that (2) of the printer (Figure 5) is pressed, whereupon the entire assembly is ready to work, except for setting the clock and calendar by pressing on the corresponding buttons (3, 4 and 5 - Figure 3) situated in the central unit. PLINTH - Given a specimen of treated glass, for example a bottle, the cover (6) of the plinth (Figure 1) is raised, which has the pressure shoe (7) fitted to it, and it is located above the drive and centring rollers (8) situating the desired start-of-measurement region on the head (9) which will retract or advance vertically depending on the diameter of the object, remaining in contact with the latter. The lid (6) is lowered, whereupon the pressure shoe (7) is situated just against the bottle, centring it and pressing it against the turning rollers. CENTRAL UNIT It allows various possibilities to be selected: Point average measurement Longitudinal average measurement Perimetral average measurement Surface average measurement (in a spiral) To select one or the other, the actuation of the switch (10 - Figure 3) for turning the centring cylinders (7 - Figure 1) is combined with the push button (9 - Figure 2) for movement of the head. If a point measurement is required to be made, the head is situated at the point to be measured by pushing on the button (1 - Figure 3) until it takes up the desired position and the red measurement button (12 - Figure 3) is pressed, whereupon the apparatus takes the measurement at the selected point and reflects it on the display (13 - Figure 3) and on the paper of the printer also indicating the date and time of the measurement. Subsequently, the head is automatically relocated in the end-of-travel rest position (14) (right or left) closest to the point at which the measurement was taken. Parallel to one of the centring rollers and of the same length, a graduated scale is fixed which makes it possible to situate the point at which the measurement was taken longitudinally. In the central unit three "high-brightness leds" are situated (16, 17 and 18 - Figure 3) indicating treatment BAND, with colours: orange (indicates treatment in high BAND), green (indicates treatment in standard BAND) and red (indicates treatment in low BAND), the latter being connected with an audible alarm. For the longitudinal average measurement it suffices to press directly on the red measurement button (12 - Figure 3), whereby the head moves automatically taking measurements, from the rest position to the opposite end of travel. The following operations are the same as in the first case. For the perimetral average measurement, the head is situated at the desired position by pressing on the button (11 - Figure 3) and subsequently the switch (10 - Figure 3), for turning the rollers; then the measurement is taken, pressing on the red measurement button (12 - Figure 3), with the same operations as in the first case. For the surface average measurement (in a spiral), it is only necessary to actuate the switch (10 - Figure 3) for turning the rollers and subsequently to press the red measurement button (12 - Figure 3), whereby the head will move automatically taking a reading from the rest position to the end of travel. The following operations are the same as in the first case. Given that the speed of advance of the head can be regulated by means of the corresponding potentiometer (20 - Figure 3), situated in the central unit, the pitch of the spiral and thereby the size of the surface area checked can be fixed at a greater or lesser size according to requirements. EXPLANATORY EXAMPLE 2 In the case of utilization of the apparatus on a production line to control and correct the treatment; the switch (10 - Figure 3) for turning the rollers as well as the red measurement button (12 - Figure 3) are replaced by a microswitch (or a reflection photocell or barrier) combined with a time-delay relay in such a way that, when the bottle withdrawn from the conveyor belt passes through the point where the microswitch is located, it pushes the stalk of the latter giving the signal to the time-delay relay which instantaneously puts the rotation of the rollers into operation and, with a defined delay (depending on the distance left between the microswitch and the site of the plinth) initiates the measurement circuit when the pusher or gripper has situated the bottle on the drive rollers of the plinth (this pusher or gripper also substitutes for the effect of the pressure rollers and cover of the laboratory equipment). At the same time as the measurement obtained is output on the screen and on the printer, the speed of the metering equipment of the treatment is regulated, the speed of which will remain fixed until the next reading. The same mechanical pusher or a pneumatic one withdraws the bottle from the plinth when the timer terminates its actuation time, leaving the apparatus prepared to receive a new object. The specimen may be withdrawn from or returned to the production line since, throughout the measurement process, it suffers no physical or chemical variation, thereby remaining at the end of the process in the same conditions in which it was withdrawn from the production line. Both the potentiometer (20 - Figure 3) for regulating the speed of the head, and the push button (11 - Figure 3) of the latter and the switch (10 - Figure 3) for turning the rollers have a corresponding operating indicator lamp (21, 22 and 23 - Figure 3). The central unit, while the apparatus is switched on, carries out a self-check in order to detect irregularities, if there are any, in its circuits, sounding the audible alarm if appropriate. The three units of the apparatus (plinth, central unit and printer) make use of systems for protection against overcurrents (varistors and fuses of appropriate value).

Claims: Apparatus arranged to measure and control the application of a surface treatment material applied onto the surface of lightened glass objects during manufacture, said manufacture involving hot and cold treatment stages, said surface treatment resulting in a non-uniform cross-linked surface distribution of said material over the surface of said glass object, and not forming a continuous film thereon, said apparatus comprising: a plinth for positioning the glass object to be measured: a head in contact with the surface of the object, said head comprising a radiation emitter illuminating the surface of an object with radiation which is linearly polarized in a plane perpendicular to the plane of incidence and the angle of incidence being chosen such that there is no reflection from those portions of the glass surface on which no treatment material is present, but reflection from those portions of the surface on which treatment material is present; a receiver receiving reflected radiation to provide a signal representative of said average density of application of said material; a central processor unit which processes the signals obtained and controls the application of said treatment material onto the surface of glass objects being manufactured in dependence on said signal so as to form said non-uniform cross-linked surface distribution, and not to form a continuous film on the surface of the objects; and a printer which records the final values of the measurements processed in the central unit. Apparatus as claimed in claim 1, wherein a polariser is provided in front of said receiver. Apparatus as claimed in claim 1 or 2, wherein a polariser is provided in said emitter. Apparatus according to Claims 1 to 3, characterized in that the plinth for fixing the position of the object to be measured allows it to be automatically centred. Apparatus according to Claim 4, characterized in that the plinth is provided with motorized movement, adjustable in speed and direction. Apparatus according to Claims 1 to 5, characterized in that the head is provided with motorized movement, adjustable in speed and direction, to allow point, longitudinal, perimetral and spiral readings, in a manual or automatic process. Apparatus according to Claims 1 to 6, wherein the emitter is controlled by the central unit intermittently in order to eliminate the effect of the ambient radiation. Apparatus according to Claims 1 to 7, wherein the receiver is arranged alternately to receive an ambient signal and an ambient signal plus a measurement signal. Apparatus according to Claims 1 to 8, characterized in that the signals recorded in the receiver of the head of the central unit are taken to a logarithmic amplifier coupled to a microprocessor which calculates and stores the differential result. Apparatus according to Claims 1 to 9, wherein the central unit includes a metering control circuit arranged to regulate the speed of the metering pumps for delivering the treatment material onto the glass surface. Apparatus according to Claims 1 to 10, wherein the metering control circuitry is also supplied with a standard signal of treatment material crosslinking density which, depending on the readings recorded in the receiver, determines the speed of the metering pumps. Apparatus according to Claims 1 to 11, characterized in that the central unit, depending on the recordings detected in the receiver and comparing them with the standard assigned value, sends out optical and/or audible alarm signals. Apparatus according to Claims 1 to 12, characterized in that the central unit displays the data measured via visual, digital or pointer-type indicators. Method of measurement and control of the application of a surface treatment material applied onto the surface of lightened glass objects during manufacture, said manufacture involving hot and cold treatment stages, said surface treatment resulting in a non-uniform cross-linked surface distribution of said material over the surface of said glass object and not forming a continuous film thereon, said method comprising (i) measuring the average density of application i.e. the amount applied per unit area, of said surface treatment material which has been applied to the surface of the glass, by the steps of: a)illuminating the surface of an object with radiation which is linearly polarized in a plane perpendicular to the plane of incidence and the angle of incidence being chosen such that there is no reflection from those portions of the glass surface on which no treatment material is present, but reflection from those portions of the surface on which treatment material is present, b)receiving reflected radiation to provide a signal representative of said average density of application of said material, c)processing said signal, and (ii)controlling the application of said treatment material onto the surface of glass objects being manufactured in dependence on said signal, so as to form said non-uniform cross-linked surface distribution, and so as not to form a continuous film on the surface of the objects.

Inventors: DE LA FUENTE FERNANDO JAVIER, DE LA FUENTE, FERNANDO, JAVIER
Applicants: FUESCA SL, FUESCA S.L.
Application year: 1994
Main classification: G01N21
IPC codes: G01N21, G01B11